High-pressure gate for photographic contact printing

ABSTRACT

A new photographic printing apparatus with which contact prints are made by exposing the original film and the printing stock material at a time when they are brought into intimate contact with one another by pneumatic pressure. The sandwich arrangement of film and printing stock is passed over a drum above which is contiguously disposed a &#39;&#39;&#39;&#39;shoe&#39;&#39;&#39;&#39; mechanism that is contoured to be partially concentric with the drum, a small or narrow air gap separating the drum and shoe whereat they are concentric. The air, under pressure, is applied to the film from the shoe side and escapes through the air gap, the entire arrangement providing the pressure distribution needed to achieve fine contact printing.

United States Patent Inventors Alvin A. Snaper 9722 Casaba Ave., Chatsworth 91311; Frank R. Gibson, 438 Lincoln Blvd., Santa Monica, Calif. 90402 Appl. No. 775,639 Filed Nov. 14, 1968 Patented Apr. 13, 1971 HIGH-PRESSURE GATE FOR PHOTOGRAPHIC CONTACT PRINTING 8 Claims, 4 Drawing Figs.

US. Cl 355/91, 355/110, 355/111 Int. Cl G03b 27/20, G03b 27/10 Field ofSearch 355/91,93,

92, 94, 87,110,111, 85,108(Inquired) [56] References Cited UNITED STATES PATENTS 3,468,606 9/ l 969 Wolf et al. 355/91 FOREIGN PATENTS 438,938 12/ l 967 Switzerland 355/92 Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard L. Moses Attorney-Allen E. Botney ABSTRACT: A new photographic printing apparatus with which contact prints are made by exposing the original film and the printing stock material at a time when they are brought into intimate contact with one another by pneumatic pressure. The sandwich arrangement of film and printing stock is passed over a drum above which is contiguously disposed a shoe mechanism that is contoured to be partially concentric with the drum, a small or narrow air gap separating the drum and shoe whereat they are concentric. The air, under pressure, is applied to the film from the shoe side and escapes through the air gap, the entire arrangement providing the pressure distribution needed to achieve fine contact printing.

HIGH-PRESSURE GATE FOR PHOTOGRAPIIIC CONTACT PRINTING The present invention relates to the photographic arts in general and more particularly relates to a photographic printing system having a high-pressure gate for contact printing.

In some photographic printing systems, contact prints are made by passing sheets or lengths of film under a source of radiant energy in intimate contact with corresponding sheets or lengths of printing stock material so that, after suitable chemical or physical processing, a copy of the subject matter contained on the original film is obtained on the printing stock, the operation being termed roll contact printing" or continuous roll contact printing." However, if the fine image detail present on the original is to be transferred to the printing stock without significant degradation, then intimate contact must be maintained between the two sheets over the area where exposure to radiant energy takes place. This condition is obtained by the application of pressure at such points.

As is well known by those familiar with the prior art, pressure may be applied by passing the film and printing stock together over a roller or drum, exposure taking place over some portion of the drums circumference, with pressure being maintained by applying tension to the ends of the rolls. By so doing, the component of force radial to the drum or roller will then supply the needed pressure. Another approach has been to pass the film and printing stock together over a transparent drum. In this case, the pressure is applied radially by rollers positioned on the circumference of the drum, and exposure is made through the transparent drum from the inside. A further approach as been to locally apply pneumatic pressure to both sides of the sandwicli" arrangement of film and printing stock.

None of the foregoing techniques has proven to be completely satisfactory, either because of inherent mechanical problems or because the incurred cost in using them has been toohigh. Accordingly, there has been a long felt need for an improved photographic printing system of the kind mentioned. The present invention fulfills this need.

It is, therefore, an object of the present invention to provide a new and improvedv high-pressure printing gate for use in photographic contact printers.

It is another object of the present invention to provide photographic printing apparatus that will ensure intimate contact between the film and the printing stock material over the area whereat exposure takes place.

It is a further object of the present invention to provide photographic printing apparatus in which pneumatic pressure maintains the film and printing stock material in intimate contact.

It is an additional object of the present invention to provide photographic printing apparatus in which a relatively high pneumatic pressure may be used without damage or wear to the printing materials or printing apparatus.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawing in which an embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only and is not intended as a definition of the limits of the invention.

FIG. I is an end view, in cross section, of a preferred embodiment of the present invention;

FIG. 2 is a side or lateral view, in cross section, of the FIG. 1 embodiment taken along the line 2-2 and in the direction of the arrows thereof;

FIG. 3 illustrates the FIG. 1 embodiment as it may be modified with the addition of fluidic elements to provide automated control of the printing operation; and

FIG. 4 illustrates a section of original film with a code recorded thereon between frames.

For a consideration of the invention in detail, reference is now made to the drawing wherein like or similar elements have been given like or similar designations throughout the several FIGS. Referring to FIGS. 1 and 2 in particular, the embodiment therein is shown to include a hollow cylindrical drum, generally designated 10, on which is contiguously disposed a shoe" that is generally designated 11, a sheet or length of original film l2 and a corresponding sheet or length of printing stock material 13 being mounted to pass between the drum and the shoe in a sandwich type arrangement. By "original film is meant film that has already been processed and which, therefore, contains the information that is to be transferred to the printing stock material which may be either unexposed film or paper. Film 12 is commonly known and referred to as the negative. As shown in the FIGS., shoe II is so contoured on its bottom surface as to be partially concentric with the lateral surface of drum 10, a small or narrow airgap 14 separating the drum and shoe whereat they are concentric.

One end of shoe 11 is mounted on a pivot 15 around which the shoe may be swiveled for purposes of adjustment, alignment and cleaning and, when in its operating position, the other end of the shoe is held against a stop 16 by a knurled nut or thumbscrew 17 mounted on a bolt 18. Stop 16 also includes an adjuster screw, and a fine adjustment of the position of the shoe at this end of it may be made by suitably setting this adjuster screw. Shoe 11 also contains a space 20 that extends across the length and width of that part of the original film that is to be printed. This space is the exposure gap and a pressure-tight window 21 is mounted above drum 10 in this exposure gap, the window being made of glass, quartz or other suitable material that is transparent to the radiant energy necessary for printing purposes. Window 21 allows such energy to pass from an exterior light source 22 through the exposure gap 20 and on to the sandwich of original film 12 and printing stock 13. As indicated in the FIGS., serrations 23 are formed in the beveled sides of the exposure gap to prevent spurious reflections of radiant energy from reaching the film since their incidence thereon would only have the effect of degrading the quality of the printed image.

When the apparatus is in operation, exposure gap 20 is pressurized by the introduction therein of a transparent gas or mixture of gases, such as air. Since the gas is trapped between the window, the shoe, the gap and the roller at this point, this produces the required pressure on the sandwich combination of elements 12 and 13. The amount of pressure that may be applied is limited only by the mechanical strength of the shoe assembly as well as the material from which the original film 12 is made. Accordingly, since adequate pressure may be applied and since the pressure is applied equally in all directions, the gas maintains the sandwich completely flat, which is certainly of very great advantage for quality printing.

Gas is provided by an exterior source, such as a pump or by tanks containing gas under pressure, and is introduced into the shoe by means of a flexible hose 24 that is coupled to the pivot 15 which may be made hollow for that purpose, namely, that of introducing the gas. Inside the shoe the gas is conducted to the exposure gap 20 by means of ducts Ila and 11b which, as is shown in FIG. 1, are coupled to pivot 15 and, therefore, to hose 24, by means of passageway 110. The gas entering ducts 11a and llb are respectively channelled to the exposure gap via passageways 11d and lle, the gas thereafter escaping into the atmosphere via the small gap 14 between the shoe and the sandwiched elements 12 and 13. By so doing, the desired gas pressure is brought to bear against these elements. Needless to say, the gap is kept as small as possible to prevent too great a loss of pressure, a spacing of about 0.007 inch being an example of what can be used.

Referring now to FIG. 2, this FIG. illustrates that apparatus according to the present invention preferably includes a step 25 at the rim ends of the drum 10 in order to prevent an excessive loss of gas at the sides of the shoe. As is also shown in this FIG., a very narrow gap 26 is inserted between the stepped portion of drum l and shoe II. This gap 26 is obviously needed to permit relative motion between the shoe and the drum but is kept very narrow, in the order of 0.003 inch, to minimize the air loss.

In the matter of drum 10, it should be noted that it is preferably hollow and constructed of a porous material, such as sintered metal, ceramic, or plastic, the purpose of this being to allow gas that may be trapped between the surface of the drum and the printing stock 13 to readily escape. This contributes to superior flatness and contact of the sandwich elements and also allows a closer fit between shoe and drum, Finally, it will be recognized that by sealing the ends of the drum, a partial vacuum may be applied to its surface by connecting a source of negative pressure, such as vacuum pump (not shown) via a hollow bearing at one end. In this way, the drum will attract the print material strongly and may even be used as a drive roller.

The pressurizing gas introduced into exposure gap may be controlled with the aid of a fluidic element, as is shown in FIG. 3 wherein a completely automated system of control is illustrated. As shown, the system includes the above-said printing light source 22 and a film code detector 27 positioned alongside or nearby an electrical power supply 28 being provided for both the light source and detector. A microswitch 29 is interposed between the power supply and the light source. As shown in FIG. I, printing light source 22 is positioned above window 21, so that the light can be projected onto the film, the microswitch 29 coupled thereto being of a kind that will, in response to a small amount of gas pressure, connect electrical power supply 28 to the light source to turn it on. Film code detector 27 is in continuous operation while the apparatus is in use and its function is to detect code indications recorded on the film I2, in response to which the detector respectively produces electrical signals.

The FIG. 3 system also includes a vacuum pump 30, a pressurized gas source 31, an electrically controlled valve 32 and, finally, a monostable fluidic amplifier element 33. Valve 32 is of the kind that normally closes a passageway but that will open up in response to an appropriate electrical signal to permit passage of the fluid involved. In the present instance, the valve is preferably of the kind that includes a timing mechanism that will automatically close the valve again after a predetermined interval of time. As for element 33, a monostable type of fluid amplifier device is shown and described in Report No. 9 of the Fluid Amplification Series periodically published by the Harry Diamond Laboratories of Washington, D.C., Report No. 9, published Mar. 8, I963, entitled Logic Elements and authored by E. V. Hobbs. On pages 8, 21 and 22 of said Report are shown and described half-adder devices which are monostable devices that can be adapted for use in the present invention.

As taught in said article, device 33 includes an inlet channel 330 through which the stream of gas flows from source 31, a pair of control channels respectively designated 33d and 33e by means of which the above-said stream of gas can be controlled so as to selectively direct the gas to one or the other of the outlet channels. Thus, inlet channel 33a connects with gas source 31, outlet channel 33b vents to ambient which, in this case, is the atmosphere, and outlet channel 33c is connected to hose 24 which, as may be seen from FIG. I, leads to the hollow of pivot 15. In the matter of control channels 33d and 33e, control channel 332 is unconnected and, therefore, is exposed to the atmosphere, whereas control channel 33d is coupled to the line or conduit connecting valve 32 to drum 10. More specifically, valve 32 is connected between vacuum pump 30 and drum 10, a tapline from the main line leading to the drum feeding into the control channel.

In order to fully understand the operation of the FIG. 3, system, it is necessary to more closely examine film 12. Accordingly, reference is made to FIG. 4 wherein a small segment of film 12 is illustrated, together with a few frames designated 12a, 12b and 12c. In accordance with the concept of the automated system contemplated here, a code of some sort is recorded on the film, preferable between the frames. As will be recognized by those skilled in the art, the code may take many forms, the one used herein for illustrative purposes being a bar 34 extending transversely across the film between frames. It is this code that film code detector is positioned .to detect and in response to which valve 32 is activated, as will more fully be explained below.

In operation, monostable fluidic device 33 is biased so that the gas stream will normally vent through outlet channel 3311, which means that the gas entering inlet channel 33a from gas source 31 will normally flow out through outlet channel 33b and, therefore, into the atmosphere. This further means that normally the gas is not supplied to exposure gap 20. Also, at this time, valve 32 is closed, which means that normally the drum I0 is not exposed to vacuum pump 30 and printing light source 22 is without power and, therefore, no light emanates from it. However, when the film code, such as a bar 34, is detected by film code detector 27, an electrical signal is applied to valve 32 which, in response thereto, opens to allow the vacuum created by vacuum pump 30 to be fully applied to drum l0 and partially applied to control channel 33d. As a result, the gas stream is diverted or flipped to outlet channel 330 and will continue to vent from this channel so long as valve 32 remains open.

With the gas stream flowing through outlet channel 330 and from thence to hose 24 and pivot 15 in shoe assembly 11, a portion of this gas is tapped off and directed to microswitch 29 which, in response to the pressure thereof, closes the switch therein to connect electrical power supply 28 to printing light source 22, thereby causing the light to go on. As previously indicated, the light is directed against the passes through window 21 to the film I2 and printing stock material 13 below, the film and the printing stock material being brought firmly together and against the surface of the drum by the combined effect of the gas pressure in exposure gap 20 and the partial vacuum in the hollow of drum [0. After it has done its job, the gas passes through airgap l4 and out of the system, the entire constructional arrangement being adapted to provide uniform gas flow and uniform pressure distribution thereof.

The timing of valve 32 is such that after the exposure of a film frame, the valve closes, thereby shutting off the vacuum supply to drum l0 and the vacuum or suction on control channel 33d. When this occurs, the gas stream flips back to outlet channel 33b and once again, therefore, the gas is vented into the atmosphere. As a result, gas pressure is no longer applied to microswitch 29 which, in response thereto, disconnects printing light source 22 from electrical power supply 28. The system is now passive again and awaiting the detection of the next code symbol on the film before going into operation again in the manner described. The absence of pressure during this period enables the drum to revolve without imposing undue friction on the film surface.

Although particular arrangements of the invention have been illustrated above by way of example, it is not intended that the invention be limited thereto. Accordingly, the invention should be considered to include any and all modifications, alterations or equivalent arrangements falling within the scope of the annexed claims.

We claim:

I. A high-pressure gate for photographic printing, said gate comprising: a cylindrical drum; apparatus mounted contiguously to the lateral surface of said drum and concentrically with a portion thereof, said apparatus being pivotally mounted at one end and including a device for fixing the other end in position, said device including means for adjusting the degree of contiguity between said drum and said apparatus, said apparatus including a space therein whereat photographic film passing between said drum and apparatus may be exposed to radiant energy, a transparent pressure-tight window mounted in and covering said space, and means within said apparatus and extending therethrough for propagating gas under pressure to said space.

2. A high-pressure gate for photographic printing, said gate comprising: a cylindrical drum; apparatus mounted contiguously to the lateral surface of said drum and concentrically with a portion thereof, said apparatus including a space therein whereat photographic film passing between said drum and apparatus may be exposed to radiant energy, the wall of said apparatus surrounding said space being beveled and serrated to prevent spurious reflections of radiant energy from reaching the film, a transparent pressure-tight window mounted in and covering said space, and means within said apparatus and extending therethrough for propagating gas under pressure to said space.

3. Ahigh-pressure gate for photographic printing, said gate comprising: a cylindrical drum; apparatus mounted contiguously to the lateral surface of said drum and concentrically with a portion thereof, said apparatus including a space therein whereat photographic film passing between said drum and apparatus may be exposed to radiant energy, a transparent pressure-tight window mounted in and covering said space, means within said apparatus and extending therethrough for propagating gas under pressure to said space, and an electro-optical and mechanical arrangement for automatically applying and releasing gas pressure to and from, respectively, the film, said arrangement including regulating means for applying the pressure during the period the film is to be exposed and for releasing it immediately thereafter.

4. The gate defined in claim 3 wherein said arrangement includes a fluidic amplifier device having two outlet channels and adapted to selectively direct a gas stream flowing therethrough to one of said two outlet channels, one outlet channel venting to the atmosphere and the other outlet channel feeding the means within said apparatus that propagates the gas to said space, and control apparatus coupled to said fluidic device to selectively direct the gas stream between said two outlet channels in accordance with the position of the film.

5. The gate defined in claim 4 wherein said fluidic device is a monostable fluidic amplifier biased to normally direct a gas stream to its outlet channel venting to the atmosphere.

6. The gate defined in claim 4 wherein said control apparatus includes pressure means for diverting the gas stream from said one to the other of said outlet channels when coupled to said fluidic device, and a valve connected between said pressure means and said fluidic device, said valve being constructed to open in response to an electrical signal and adapted to close a set time thereafter.

7. The gate defined in claim 6 wherein said control apparatus further includes a film code detector for generating an electrical signal when a frame on the film is to be exposed for printing purposes, said detector being coupled to said valve and applying said electrical signal thereto.

8. The gate defined in claim 7 wherein said gate further includes exposure means comprising a printing light source that is selectively operable, and a pressure-sensitive microswitch coupled between said light source and the other outlet channel of said fluidic amplifier device, said microswitch operating said light source when gas flows through said other outlet channel. 

1. A high-pressure gate for photographic printing, said gate comprising: a cylindrical drum; apparatus mounted contiguously to the lateral surface of said drum and concentrically with a portion thereof, said apparatus being pivotally mounted at one end and including a device for fixing the other end in position, said device including means for adjusting the degree of contiguity between said drum and said apparatus, said apparatus including a space therein whereat photographic film passing between said drum and apparatus may be exposed to radiant energy, a transparent pressure-tight window mounted in and covering said space, and means within said apparatus and extending therethrough for propagating gas under pressure to said space.
 2. A high-pressure gate for photographic printing, said gate comprising: a cylindrical drum; apparatus mounted contiguously to the lateral surface of said drum and concentrically with a portion thereof, said apparatus including a space therein whereat photographic film passing between said drum and apparatus may be exposed to radiant energy, the wall of said apparatus surrounding said space being beveled and serrated to prevent spurious reflections of radiant energy from reaching the film, a transparent pressure-tight window mounted in and covering said space, and means within said apparatus and extending therethrough for propagating gas under pressure to said space.
 3. A high-pressure gate for photographic printing, said gate comprising: a cylindrical drum; apparatus mounted contiguously to the lateral surface of said drum and concentrically with a portion thereof, said apparatus including a space therein whereat photographic film passing between said drum and apparatus may be exposed to radiant energy, a transparent pressure-tight window mounted in and covering said space, means within said apparatus and extending therethrough for propagating gas under pressure to said space, and an electro-optical and mechanical arrangement for automatically applying and releasing gas pressure to and from, respectively, the film, said arrangement including regulating means for applying the pressure during the period the film is to be exposed and for releasing it immediately thereafter.
 4. The gate defined in claim 3 wherein said arrangement includes a fluidic amplifier device having two outlet channels and adapted to selectively Direct a gas stream flowing therethrough to one of said two outlet channels, one outlet channel venting to the atmosphere and the other outlet channel feeding the means within said apparatus that propagates the gas to said space, and control apparatus coupled to said fluidic device to selectively direct the gas stream between said two outlet channels in accordance with the position of the film.
 5. The gate defined in claim 4 wherein said fluidic device is a monostable fluidic amplifier biased to normally direct a gas stream to its outlet channel venting to the atmosphere.
 6. The gate defined in claim 4 wherein said control apparatus includes pressure means for diverting the gas stream from said one to the other of said outlet channels when coupled to said fluidic device, and a valve connected between said pressure means and said fluidic device, said valve being constructed to open in response to an electrical signal and adapted to close a set time thereafter.
 7. The gate defined in claim 6 wherein said control apparatus further includes a film code detector for generating an electrical signal when a frame on the film is to be exposed for printing purposes, said detector being coupled to said valve and applying said electrical signal thereto.
 8. The gate defined in claim 7 wherein said gate further includes exposure means comprising a printing light source that is selectively operable, and a pressure-sensitive microswitch coupled between said light source and the other outlet channel of said fluidic amplifier device, said microswitch operating said light source when gas flows through said other outlet channel. 